Catheter having an auxiliary lumen for use with a functional measurement wire

ABSTRACT

The present invention relates to a surgical catheter, and more particularly, a balloon catheter having an auxiliary lumen configured to permit the advancement of a functional measurement wire to a treatment site. The auxiliary lumen communicates with a working lumen that is configured to permit the advancement of a guidewire and the functional measurement wire, so that the guidewire and functional measurement wire may selectively be advanced to the treatment site during a surgical procedure.

FIELD OF THE INVENTION

The present invention relates to a surgical catheter, and moreparticularly, a balloon catheter having an auxiliary lumen configured topermit the advancement of a functional measurement wire to a treatmentsite.

BACKGROUND OF THE INVENTION

Balloon angioplasty is a widely used technique for treating vasculardisease. In balloon angioplasty, a catheter having an inflatable balloonaffixed to its distal end is guided through a patient's vasculature withthe balloon in a deflated state, and the balloon is positioned within avascular lesion. The balloon then is inflated to compress theatherosclerotic plaque against the vessel wall to restore adequate bloodflow in the vessel.

It may be desirable to obtain various physiological measurements nearthe treatment site before, during or after an intravascular surgicalprocedure, such as balloon angioplasty. For example, it may be useful toobtain pressure or flow measurements near the site of a vascularocclusion. It may be beneficial to readily obtain such measurements atany time during the surgical procedure to assess the efficacy of theprocedure.

One previously known method of placing a functional measurement wire ata treatment site is to exchange the functional measurement wire for theguide wire, i.e., to fully withdraw the guide wire from the vessel andthen insert the functional measurement wire in place of the guide wire.Once the measurement is taken, the functional measurement wire iswithdrawn and the guidewire reinserted. Such a method can be cumbersomeand time-consuming, especially where it is desired to take multiplemeasurements during the course of a procedure.

Alternatively, a separate lumen may be provided in the catheter toaccommodate the functional measurement wire, but this solution requiresan increase in the catheter profile. Such an increase in profile,especially at the distal end of the catheter, may undesirably limitapplicability of the device in smaller vessels, and also may result inan increase in the stiffness of the distal region of the catheter,thereby making it more difficult to negotiate tortuous anatomy.

Other alternative approaches are known in the art. For example, U.S.Pat. No. 5,921,957 to Killion et al. describes a balloon dilatationcatheter having a guidewire lumen, and an atraumatic tip at the distalend of the catheter having an aperture that the guidewire passesthrough. The diameter of the aperture matches the diameter of theguidewire used in the procedure. The inner diameter of the guidewirelumen is described as substantially larger than the guidewire diameterused in the procedure, which creates a space between the guidewire andthe guidewire lumen. In this available space, dye injections andpressure measurements may be performed via holes in the atraumatic tipthat are disposed just proximal to the aperture. Accordingly, when theguidewire extends through the aperture, pressure measurements may beobtained via the extra space provided in the guidewire lumen and theholes in the atraumatic tip.

A main drawback associated with the device described in the Killionpatent is that, in order to take pressure measurements through theguidewire lumen, the guidewire lumen must be relatively large to providethe additional lumen space that is required. By increasing the innerdiameter of the guidewire lumen, the stiffness of the device isundesirably increased, and may render the device unsuitable for use insmaller vessels.

Still other previously-known devices have incorporated the use of aslit, port or frangible wall disposed in a lateral surface of thecatheter that communicates with a guidewire lumen. For example, U.S.Pat. No. 5,921,971 to Agro et al. describes a catheter having aguidewire lumen extending along the catheter, wherein a slit in thecatheter shaft allows a guidewire to be introduced into the guidewirelumen. The catheter further comprises two ancillary lumens that extendlongitudinally along the length of the catheter.

One drawback associated with the device described in the Agro patent isthat the guidewire may not be easily used in combination with otherdevices, such as a functional measurement wire, without removing theguidewire from the side slit and then introducing the measurement wire.Although the functional measurement wire alternatively may be introducedinto one of the ancillary lumens, an increase in catheter profile occurswhen providing a guidewire and functional measurement wiresimultaneously at the distal end of the catheter.

In view of these disadvantages of previously known catheters, it wouldbe desirable to provide a catheter that may be used in conjunction witha functional measurement wire to obtain measurements near a vasculartreatment site.

It also would be desirable to provide a catheter that readily mayintroduce either a guidewire or a functional measurement wire to avascular treatment site.

It further would be desirable to provide a catheter that readily mayadvance either a guidewire or a functional measurement wire to avascular treatment site while maintaining a minimal distal catheterprofile.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of this invention to provide acatheter that may be used in conjunction with a functional measurementwire to obtain measurements near a vascular treatment site.

It is also an object of this invention to provide a catheter thatreadily may introduce either a guidewire or a functional measurementwire to a vascular treatment site.

It is a further object of the present invention to provide a catheterthat readily may advance either a guidewire or a functional measurementwire to a vascular treatment site while maintaining a minimal distalcatheter profile.

These and other objects of the present invention are accomplished byproviding a balloon catheter having an auxiliary lumen configured topermit a functional measurement wire to be selectively advanced to atreatment site. The auxiliary lumen communicates with a working lumen,and is configured to permit the advancement of either a guidewire or thefunctional measurement wire.

In a preferred embodiment, the apparatus comprises a catheter having anouter tube and an inner tube, each having proximal and distal ends. Theinner tube comprises a working lumen extending therethrough and isdisposed within the outer tube along the length of the catheter. Theapparatus further comprises an auxiliary tube having an auxiliary lumenthat is in communication with a side port disposed in a lateral surfaceof the outer tube near the distal end. The distal end of the auxiliarylumen communicates with the working lumen via a bifurcation. Theapparatus further preferably comprises an inflatable member disposed atthe distal end of the catheter that is in fluid communication with aninflation lumen formed between the inner tube and the outer tube.

The auxiliary lumen is configured to permit the selective advancement ofa functional measurement wire to a treatment site via a distal portionof the working lumen. In a preferred method, a proximal end of thefunctional measurement wire is loaded into the distal portion of theworking lumen, then directed into the auxiliary lumen. The functionalmeasurement wire then is retracted proximally until a distal end of thefunctional measurement wire is positioned within the auxiliary lumen,preferably at a location just proximal of the bifurcation between theauxiliary lumen and the working lumen. A proximal portion of thefunctional measurement wire extends out of the side port in the outertube and resides in the vessel, with the proximal end of the functionalmeasurement wire disposed outside the patient's body for manipulation bythe physician.

During a medical procedure, the catheter is advanced over a guidewire,via the working lumen of the catheter, to a treatment site. Theguidewire then may be retracted proximally, so that its distal end isdisposed proximal of the bifurcation. The functional measurement wirethen may be advanced distally to the treatment site via the distalportion of the working lumen. The functional measurement wireaccordingly may be advanced to the treatment site to take desiredmeasurements, for example, pressure or flow measurements, before, duringor after an intravascular procedure, without a full exchange of theguide wire and without the need for a separate lumen for the functionalmeasurement wire in the proximal portion of the catheter.

Methods of loading the functional measurement wire into the auxiliarylumen prior to the intravascular procedure, so that the functionalmeasurement wire readily may be advanced to a treatment site during theprocedure, also are provided.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the invention, its nature and various advantageswill be apparent from the accompanying drawings and the followingdetailed description of the preferred embodiments, in which:

FIGS. 1A-1C are, respectively, a side view of the apparatus of thepresent invention, and side sectional views of central and distalportions of the apparatus;

FIGS. 2A-2B are, respectively, cross-sectional views along line A-A andline B-B of FIG. 1B;

FIGS. 3A-3C are side sectional views depicting a method for loading afunctional measurement wire into an auxiliary lumen of the presentinvention;

FIGS. 4A-4C are side sectional views depicting an alternative method forloading a functional measurement wire into an auxiliary lumen of thepresent invention;

FIGS. 5A-5B are side sectional views depicting yet a further alternativemethod for loading a functional measurement wire into an auxiliary lumenof the present invention;

FIGS. 6A-6B are side sectional views depicting the selective use of thefunctional measurement wire in accordance with the present invention;and

FIGS. 7A-7B are enlarged views of the schematics in FIGS. 6A-6B,respectively.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a therapeutic catheter, such as aballoon angioplasty catheter or stent delivery system, and methods thatallow the advancement of a functional measurement wire to a treatmentsite using an auxiliary lumen of the catheter. In accordance with theprinciples of the present invention, the catheter comprises an outertube, and an inner tube disposed within the outer tube that bifurcatesfrom a working lumen into an auxiliary lumen configured to permit theadvancement of the functional measurement wire. Because the auxiliarylumen merges with the working lumen, the functional measurement wire maybe introduced before, during or after a surgical procedure in aconvenient manner without causing an increased distal catheter profile.

Referring to FIG. 1, apparatus 10 of the present invention preferablycomprises balloon catheter 12 having proximal end 14 and distal end 16.Balloon catheter 12 comprises outer tube 20 and inner tube 22, eachhaving proximal and distal ends, as shown in FIG. 1B. Inner tube 22 isdisposed within outer tube 20, and the annulus between outer tube 20 andinner tube 22 forms inflation lumen 25. Inner tube 22 comprises workinglumen 26 that extends from proximal end 14 of catheter 12 to distal end16. At proximal end 14, working lumen 26 is coupled to guidewire port17, while inflation lumen 25 is coupled to inflation port 19. Guidewireport 17 and inflation port 19 may be constructed in manners that are perse known in the art.

In accordance with principles of the present invention, inner tube 22includes bifurcation 23 where inner tube 22 converges with auxiliarytube 24. Auxiliary tube 24 has proximal and distal ends and auxiliarylumen 28 extending therethrough. Auxiliary lumen 28 is in communicationwith working lumen 26 of inner tube 22 at the distal end, while theproximal end of auxiliary lumen 28 is in communication with side port30, which is disposed in a lateral surface of outer tube 20, as shown inFIG. 1B.

As described in detail with respect to FIGS. 6-7 hereinbelow, auxiliarylumen 28 is sized to permit the advancement of a functional measurementwire, e.g., a wire having a pressure or flow sensor disposed at a distalend. Working lumen 26 comprises a proximal portion disposed proximal ofbifurcation 23, and a distal portion disposed distal of bifurcation 23,as shown in FIG. 1B. The proximal portion of working lumen 26 is sizedto permit the advancement of a guidewire, while the distal portion issized to permit the advancement of either a guidewire or a functionalmeasurement wire to the site of an occlusion.

The distal end of inner tube 22 preferably is affixed to a distal end ofballoon 32, as shown in FIG. 1C, while a proximal end of balloon 32 isaffixed to the distal end of outer tube 20. Occlusion balloon 32 may beconstructed in accordance with balloon catheters that are per se knownin the art, e.g., using a compliant or semi-compliant material, such aspolyurethane, latex or polyisoprene. Additionally, inner tube 22 maycomprise at least one radiopaque marker (not shown) that is disposedwithin balloon 32 to facilitate positioning of distal end 16 in apatient's vasculature.

Referring to FIG. 2, two cross-sectional views of catheter 12 areprovided. FIG. 2A depicts a cross-sectional view along line A-A of FIG.1B, wherein inner tube 22 is disposed within outer tube 20. Inner tube22 comprises working lumen 26 that is sized to permit selectivelongitudinal advancement of either a guidewire or a functionalmeasurement wire. An annulus between inner tube 22 and outer tube 20forms inflation lumen 25.

In FIG. 2B, a cross-sectional view along line B-B of FIG. 1B isprovided, wherein inner tube 22 and auxiliary tube 24 are disposedwithin outer tube 20. Spaces between outer tube 20, inner tube 22 andauxiliary tube 24 form inflation lumen 25 in this region. Auxiliary tube24 comprises auxiliary lumen 28 that is sized to permit the longitudinaladvancement of a functional measurement wire.

In a preferred embodiment of the present invention, the outer diameterof outer tube 20 along section A-A is about 2.7 F (about 0.9 mm), whilethe outer diameter of outer tube 20 along section B-B is about 3.2 F(about 1.05 mm). As shown in FIG. 1B, outer tube 20 preferably comprisesproximal taper 32 and distal taper 34 to accommodate the additionaldiameter provided by auxiliary tube 24.

Lumen 26 preferably is sized to accommodate a standard 0.014 in. (0.36mm) guidewire, while auxiliary lumen may be sized to accept apreviously-known functional measurement wire, such as the FloWire.®.flow measurement wire or WaveWire.®. pressure measurement wire offeredby Jomed, Inc., Rancho Cordova, Calif. Auxiliary lumen 28 preferably hasa length, e.g., 5 to 10 cm, sufficient to prevent the distal end of thefunctional measurement wire from slipping out of the auxiliary lumenwhen the distal end of the functional measurement wire is parkedtherein.

Catheter 10 may in addition comprise a stylet, discussed below withrespect to FIGS. 3 and 4, to facilitate initial placement of thefunctional measurement wire in the auxiliary lumen.

Referring now to FIG. 3, a preferred method of using catheter 12 incombination with a functional measurement wire is described. In a firststep, stylet 50 having proximal and distal ends and receptor 52 coupledto the distal end is partially disposed within auxiliary lumen 28, asshown in FIG. 3A. The distal end of stylet 50, including receptor 52, isloaded into region 56 of inner tube 22, which is situated just distal tobifurcation 23. Region 56 comprises a slightly larger inner diameterrelative to the inner diameter of working lumen 26, to accommodate forthe bifurcation from working lumen 26 into two separate lumens. Outertube 20 and inner tube 22 preferably comprise circumferential tapers 60and 58, respectively, that provide a transition to the slightly largerdiameter at region 56.

When receptor 52 is disposed within region 56 of inner tube 22, theproximal end of stylet 50 exits auxiliary lumen 28 at side port 30 ofouter tube 20, as shown in FIG. 3A. This enables a physician tomanipulate the proximal end of stylet 50, while the distal end havingreceptor 52 remains disposed within region 56. In a preferredembodiment, an outer portion of receptor 52 is sized to engage an innerwall of region 56 so that minimal friction holds receptor 52 in place,but so that relatively small forces may overcome the friction andproximally retract receptor 52.

In a next step, functional measurement wire 54 having proximal anddistal ends is provided. As shown in FIG. 3A, the proximal end offunctional measurement wire 54 is loaded into the distal portion ofworking lumen 26 at the distal end of catheter 12. The proximal end offunctional measurement wire 54 then is advanced proximally within thedistal portion of working lumen 26 until it engages an inner surface ofreceptor 52, as shown in FIG. 2B. The inner surface of receptor 52 maycomprise an adhesive or mechanical engagement configured to engage theproximal end of functional measurement wire 54. Once engaged, aphysician may retract an exposed portion of stylet 50 proximally, whichin turn will proximally retract receptor 52 and functional measurementwire 54. Receptor 52 may comprise proximal taper 53 that ensures thatreceptor 52 does not snag at bifurcation 23, but rather is guidedsmoothly into auxiliary lumen 28.

Once the distal end of functional measurement wire 54 has been guidedinto auxiliary lumen 28, as shown in FIG. 3C, the proximal end offunctional measurement wire 54 may be disengaged from the inner surfaceof receptor 52 and coupled to its appropriate measurement circuitry.Functional measurement wire 54 is thus parked within auxiliary lumen 28so that it readily may be advanced in a distal direction into the distalportion of working lumen 26, and extended into a vascular treatment siteto obtain desired measurements.

Referring to FIG. 4, an alternative method for loading functionalmeasurement wire 54 into auxiliary lumen 28 is described. In FIG. 4A,catheter 12 comprises tubular member 70 that preferably is fixedlydisposed substantially within a region of taper 34, and provides atransition between the distal portion of working lumen 26 and auxiliarylumen 28, as shown in FIG. 4A.

In FIG. 4A, the proximal end of functional measurement wire 54 is loadedinto the distal portion of working lumen 26 at distal end 16 of catheter12. The proximal end of functional measurement wire 54 then is advancedproximally within the distal portion of catheter 12. When the proximalend of functional measurement wire 54 is just distal to bifurcation 23,a portion of outer tube 20 near taper 34 may be compressed, e.g.,manually, as shown in FIG. 4B. Compressive force F may be sufficient tocollapse a local portion of working lumen 26 without displacing tubularmember 70, which preferably is relatively rigid. This effectively closesbifurcation 23 and causes the distal portion of working lumen 26 tocommunicate exclusively with auxiliary lumen 28, as shown in FIG. 4B.

The proximal end of functional measurement wire 54 then may be beenguided through tubular member 70 into auxiliary lumen 28, andcompressive force F may be removed so catheter 12 returns to itsoriginal shape of FIG. 4A. Functional measurement wire 54 then may beretracted proximally until the distal end of functional measurement wire54 is disposed just proximal of bifurcation 23, as shown in FIG. 4C. Inuse, functional measurement wire 54 readily may be advanced in a distaldirection through tubular member 70 and into the distal portion ofworking lumen 26, then extended into treatment site near the distal endof catheter 12.

Referring to FIG. 5, a further alternative method for loading functionalmeasurement wire 54 into auxiliary lumen 28 is described. In FIG. 5A,stylet 80 having proximal and distal ends and guiding member 82 coupledto the distal end is provided in the proximal portion of working lumen26. The distal end of stylet 80 is loaded into the proximal portion ofworking lumen 26 and is advanced distally so that guiding member 82preferably is disposed just proximal to bifurcation 23, as shown in FIG.5A.

The proximal end of functional measurement wire 54 then may be loadedinto the distal portion of working lumen 26 at distal end 16 of catheter12. When functional measurement wire 54 then is advanced proximallytoward bifurcation 23, the proximal end of functional measurement wire54 will be diverted into auxiliary lumen 28 via guiding member 82, asshown in FIG. 5A. Functional measurement wire 54 may be retractedproximally until the distal end of functional measurement wire 54 isdisposed just proximal of bifurcation 23, as shown in FIG. 5B. Stylet 80having guiding member 82 then may be removed from the proximal portionof working lumen 26.

The techniques described in FIGS. 3-5 hereinabove describe methods forloading functional measurement wire 54 into auxiliary lumen 28, so thatfunctional measurement wire 54 readily may be advanced into the distalportion of the working lumen 26 and to a treatment site. It may beappreciated that functional measurement wire 54 also may be loaded intoauxiliary lumen 28 using other techniques that are not illustrated. Forexample, the distal end of functional measurement wire 54 may be loadedinto side port 30, then distally advanced within auxiliary lumen 28until the distal end of functional measurement wire 54 is positionedjust proximal of bifurcation 23.

Referring to FIG. 6, a method for using the apparatus of the presentinvention during an intravascular procedure is described. In a firststep, functional measurement wire 54 may be loaded into auxiliary lumen28 and disposed just proximal to bifurcation 23, e.g., using one of thetechniques described hereinabove with respect to FIGS. 3-5. Then,guidewire 100 having proximal and distal ends is provided, and thedistal end of guidewire 100 is introduced into the patient's vasculatureusing techniques that are per se known in the art. The distal end ofguidewire 100 then navigates a patient's vasculature and ultimately isdisposed at a treatment site.

A physician then may advance the distal portion of working lumen 26 overthe proximal end of guidewire 100, then distally advance catheter 12 tothe vascular treatment site via guidewire 100. Once distal end 16 ofcatheter 12 is properly positioned, e.g., when balloon 32 is disposedwithin a stenosis, then balloon 32 may be inflated via inflation port 19and inflation lumen 25.

Prior to inflation of balloon 32, or any time thereafter, a physicianmay obtain desired measurements at the treatment site using functionalmeasurement wire 54. When measurements are desired, guidewire 100 may beretracted proximally within working lumen 26 until the distal end ofguidewire 100 is positioned within a proximal portion of working lumen26 located just proximal of bifurcation 23, as shown in FIG. 6B.

At this time, functional measurement wire 54 then may be advanceddistally into the distal portion of working lumen 26 and toward distalend 16 of catheter 12, as shown in FIG. 6B. The distal end of functionalmeasurement wire 54 may be advanced distal to catheter 12 via workinglumen 26, to take the desired measurements near the treatment site. Forexample, functional measurement wire 54 may comprise a pressure or flowsensor at the distal end that enables pressure measurements to beobtained near a treatment site before, during or after an angioplastyprocedure involving balloon 32.

Referring to FIG. 7, a detailed schematic of FIG. 6 near bifurcation 23is provided. In FIG. 7A, the distal end of functional measurement wire54 is disposed within auxiliary lumen 28 at a location just proximal ofbifurcation 23, e.g., according to one of the techniques describedhereinabove with respect to FIGS. 3-5. A physician then may advanceguidewire 100 to a vascular treatment site, then advance catheter 12over guidewire 100 to the treatment site. Guidewire 100 then may beretracted proximally within working lumen 26 to a location just proximalof bifurcation 23, as shown in FIG. 7B.

Functional measurement wire 54 then may be advanced distally into thedistal portion of working lumen 26 and toward the vascular treatmentsite, as shown in FIG. 7B. Taper 35, which provides a transition betweeninner tube 22 and auxiliary tube 24, facilitates guidance of functionalmeasurement wire 54 into the distal portion of working lumen 26.Circumferential taper 58 of inner tube 22 further facilitates guidanceof functional measurement wire 54 into the distal portion of workinglumen 26, so that functional measurement wire 54 may be advanceddistally to the vascular treatment site to obtain desired measurements.

Advantageously, after obtaining the desired measurements, functionalmeasurement wire 54 may be retracted proximally and disposed in itsoriginal position within auxiliary lumen 28, as shown in FIG. 7A.Guidewire 100 then may be advanced distally into the distal portion ofworking lumen 26 and to the vascular treatment site, for example, toreposition distal end 16 of catheter 12 during the surgical procedure.In effect, the apparatus of the present invention allows both functionalmeasurement wire 54 and guidewire 100 to be selectively advanced to atreatment site, to facilitate positioning of catheter 12 during asurgical procedure and efficiently obtain desired measurements at atreatment site.

While preferred illustrative embodiments of the invention are describedabove, it will be apparent to one skilled in the art that variouschanges and modifications may be made therein without departing from theinvention. The appended claims are intended to cover all such changesand modifications that fall within the true spirit and scope of theinvention.

1. An apparatus for facilitating the advancement of a functionalmeasurement wire to a vascular treatment site, the apparatus comprising:an outer tube having proximal and distal ends; an inner tube havingproximal and distal ends and a working lumen extending therethrough, theinner tube being disposed within the outer tube; and an auxiliary tubehaving proximal and distal ends and an auxiliary lumen extendingtherethrough, wherein the auxiliary lumen communicates at the proximalend with a side port disposed in a lateral surface of the outer tube andat a distal end communicates with the working lumen of the inner tube todefine a bifurcation, wherein the auxiliary lumen is configured topermit the selective advancement of a functional measurement wire to atreatment site via a distal portion of the working lumen that is distalto the bifurcation.
 2. The apparatus of claim 1 wherein a space betweenthe inner tube and the outer tube forms an inflation lumen.
 3. Theapparatus of claim 2 further comprising a balloon affixed at a proximalpoint to the distal end of the outer tube and further affixed at adistal point to the distal end of the inner tube, wherein the balloon isin fluid communication with the inflation lumen.
 4. The apparatus ofclaim 1 wherein the distal portion of the working lumen is configured topermit the longitudinal advancement of a guidewire.
 5. The apparatus ofclaim 1 wherein the distal portion of the working lumen is configured topermit the longitudinal advancement of a functional measurement wire. 6.The apparatus of claim 1 further comprising a stylet having proximal anddistal ends, and a receptor coupled to the distal end, wherein thereceptor is adapted to engage a proximal end of the functionalmeasurement wire to assist in positioning the functional measurementwire within the auxiliary lumen.
 7. The apparatus of claim 6 wherein thereceptor is adapted to be disposed in a region of inner tube that issituated just distal to the bifurcation.
 8. The apparatus of claim 1further comprising a tubular member that is fixedly disposedsubstantially within the auxiliary lumen at a location that is justproximal to the bifurcation.
 9. The apparatus of claim 1 furthercomprising a stylet having proximal and distal ends and a guiding membercoupled to the distal end, wherein the distal end of the stylet isconfigured to be advanced into a proximal end of the working lumen. 10.The apparatus of claim 9 wherein the guiding member is configured todirect a proximal end of the functional measurement wire into theauxiliary lumen.
 11. The apparatus of claim 1 further comprising a taperthat provides a transition between the inner tube and the auxiliarytube, the taper configured to facilitate the distal advancement of thefunctional measurement wire from the auxiliary lumen into the distalportion of the working lumen.
 12. The apparatus of claim 1 furthercomprising a circumferential taper disposed just distal to thebifurcation, the circumferential taper configured to facilitate thedistal advancement of the functional measurement wire from the auxiliarylumen into the distal portion of the working lumen.
 13. The apparatus ofclaim 1 further comprising a functional measurement wire adapted toprovide pressure or flow measurements.
 14. A method for facilitating theadvancement of a functional measurement wire to a vascular treatmentsite, the method comprising: providing apparatus comprising an outertube having proximal and distal ends, an inner tube having proximal anddistal ends and a working lumen extending therethrough, wherein theinner tube is disposed within the outer tube, and an auxiliary tubehaving proximal and distal ends and an auxiliary lumen extendingtherethrough, wherein the auxiliary lumen communicates at a proximal endwith a side port disposed in a lateral surface of the outer tube and ata distal end communicates with the working lumen of the inner tube todefine a bifurcation; positioning a functional measurement wire withinthe auxiliary lumen; advancing the apparatus to a treatment site over aguidewire disposed within the working lumen; retracting the guidewirewithin the working lumen to a location proximal of the bifurcation; andselectively advancing the functional measurement wire into the workinglumen to obtain measurements near the treatment site.
 15. The method ofclaim 14 wherein positioning the functional measurement wire within theauxiliary lumen further comprises: providing a stylet having proximaland distal ends a receptor coupled to the distal end; loading the distalend of the stylet into the side port and disposing the distal endsubstantially within the working lumen; causing the proximal end of thefunctional measurement wire to engage the receptor; and proximallyretracting the stylet to cause the functional measurement wire to beguided into the auxiliary lumen.
 16. The method of claim 14 whereinpositioning the functional measurement wire within the auxiliary lumenfurther comprises: providing a stylet having proximal and distal ends aguiding member coupled to the distal end; positioning the guiding memberwithin the working lumen at a position just proximal of the bifurcation;and causing the proximal end of the functional measurement wire to bedirected into the auxiliary lumen.
 17. The method of claim 14 whereinpositioning the functional measurement wire within the auxiliary lumenfurther comprises: providing a tubular member that is fixedly disposedsubstantially within the auxiliary lumen at a location just proximal ofthe bifurcation; and causing the proximal end of the functionalmeasurement wire to be advanced through the tubular member and directedinto the auxiliary lumen.
 18. The method of claim 17 wherein causing theproximal end of the functional measurement wire to be advanced throughthe tubular member and directed into the auxiliary lumen comprisescompressing the outer tube near the bifurcation.
 19. The method of claim14 wherein positioning the functional measurement wire within theauxiliary lumen further comprises: advancing a distal end of thefunctional measurement wire into the auxiliary lumen via the side port;and distally advancing the distal end of the functional measurement wirewithin the auxiliary lumen.
 20. The method of claim 14 wherein obtainingmeasurements near the treatment site includes obtaining pressuremeasurements.